The subroadbed of Free-mo modules is
typically the module top, either extending across the full width of the
module or following some form of a “cookie cutter” approach.The module framework and subroadbed are the foundations upon
which good trackwork depends.While invisible in the finished module, finished trackwork will
inevitably expose the framework’s and
sub-roadbed’s faults.Whether made of foam, plywood, splines or other material, the framework
and sub-roadbed must satisfy the following:

1. Use module frame materials that are strong, stable, warp free and
resistant to expansion or contraction with humidity and temperature.

This is extremely important and will
cause continual problems if ignored.Avoid
use of MDF. MDF is very heavy, not
particularly strong, and is affected by humidity. A
material you can’t go wrong with is high ply-count Baltic or Finn birch
plywood.It’s important to
use material of sufficient thickness for the frame member involved.

2.The subroadbed must be flat, level and perpendicular to the end
plates of the module.

This 3-dimensional requirement is
absolutely fundamental to successful module creation.

1st dimension:End plates must be
exactly perpendicular to the subroadbed.It’s essential to read and follow Gregg Fuhriman’s advice in
Appendix 2.

2nd
dimension:The subroadbed (usually the module top) must be level from side-to-side
with the endplate. At a setup either the track or
the end plate will be used to determine if a module is level.Out-of-level subroadbed will force a twist in the track at the bridge
rails or make it impossible to match up the endplates nicely with
adjoining modules.

3rd
dimension:The subroadbed must not slope down or rise up at the module end.The most common module design has the top of the module extending
to, but not over, the top of the endplate.Any mismatch of the module top and the top of the endplate will
likely result in a problem.

A better
approach is to run the top of the subroadbed over the top of the end
plate.

If the top edge of the endplate is high
relative to the module top, the only solution is to reduce the top edge
of the endplate.Failing to
do so will result in an upward rise in the track at the end of the module.

If the top edge of the endplate is low
relative to the module top, there simply isn’t a good solution.Sanding the module top to match the endplate will result in a
downward dip in the track
at the module end.

Example:The
distance from the pilot and the front truck kingpin of an Alco PA-1 and
super-detailed plastic engine is long enough that the pilot and snowplow move up and down quite
a lot as the locomotives travel through dips and rises in trackwork.At a “V” shaped dip at a module joint, metal pilots or plows
contact the track and cause a short.

Example:The use of prototypical size couplers on long cars can result in
uncoupling as the couplers rise and fall relative to each other on track
that isn’t level through the bridge rails.

3.The subroadbed at each
end of the module must be level with the roadbed at the other end.

Any twist of the subroadbed from one end
of a module to the other will result in twist in the track at the bridge
rails at one or the other end of the module or will force twisting of
the whole module at the setup.

Example:At a recent setup, a twist at the bridge
rails resulted from a difference in side-to-side leveling of the
subroadbed even though the endplates of the adjoining modules were level with each other.The result was that some C-C locomotives would derail since the
twist across the bridge rails was so short and pronounced.

The
only solution would be to level the track at the module ends which would
result in an unsightly mismatch of the endplates.

4.Unless there is a grade
included in the module, the
sub-roadbed should be flat and level across the length of the module.

This means truly flat and truly
level.Use a straight edge
and sight along the module to make sure that the sub-roadbed is truly
flat.Support the
subroadbed well and securely along its length to make sure that it will
stay flat and level over time. There
are Free-mo modules that are 15 years or more old and have been subjected
to a lot of handling and transportation.Some have held up well; others haven’t
lasted so well.

5.If there is a transition to a grade
included in the module, employ
vertical curves that are extremely gradual (very large radius) between
the level and the inclined track.

Too abrupt a transition will result in
derailments, mismatched couplers, and will look un-prototypical.The steeper the grade, the longer the vertical curve needs to be.If in doubt at all, make vertical curves of extremely large
radius.The
Northern California Free-mo recommendation for vertical
curves is described in
Appendix 5.

Remember that transitions in track level
(e.g., from HO roadbed to N roadbed or to the subroadbed) are grades and
must be long and gradual.See item 4 in the
handbook section on roadbed.